In a liquid crystal display (LCD) device, a TFT substrate over which pixel electrodes and thin-film transistors, inter alia, are formed in a matrix and an opposing substrate over which color filters, inter alia, are formed in positions corresponding to the pixel electrodes in the TFT substrate are placed facing each other and liquid crystals are sandwiched between the TFT substrate and the opposing substrate. An image is produced by controlling light transmissibility through liquid crystal modules pixel by pixel.
Owing to the fact that LCD devices are flat and light, they are used in an increasing wide range of applications in various fields including a large-screen display of TV and the like, mobile phones, Digital Still Camera (DSC), etc. Meanwhile, viewing angles are a problem specific to LCD devices. Viewing angles imply a phenomenon in which brightness and chromaticity change depending on when the screen is viewed squarely and when viewed from an oblique direction. An In Plane Switching (IPS) type LCD in which liquid crystal molecules are moved by applying an electric field in a horizontal direction offers superior viewing angle performance.
As an LC alignment process applied for alignment films for use in an LCD device, that is, a method for providing the alignment films with the capability of LC alignment control, rubbing is a conventionally used method. The LC alignment process by this rubbing accomplishes alignment of liquid crystals by rubbing the alignment films with a cloth. An alternative method for providing the alignment films with the capability of LC alignment control without touching the alignment films is called a photo-alignment method. Because liquid crystals in the IPS type LCD do not need to have a pretilt angle, the photo-alignment method can be applied to the IPS type LCD.
A photo-alignment process, namely, a photolytic LC alignment by irradiation of light such as, typically, ultraviolet light is disclosed in Japanese Published Unexamined Patent Application No. 2004-206091, in which the following are described about the photo-alignment process of photolytic LC alignment: (1) this process decreases the disturbance of LC alignment due to a complex level difference configuration in a pixel region; and (2) this process eliminates thin-film transistor breakdown caused by static electricity generated In the LC alignment process by rubbing and a poor-quality display caused by the disturbance of LC alignment due to pilling of the rubbing cloth or dust attached thereto and also eliminates process complexity because of frequent rubbing cloth replacement required to obtain the capability of uniform LC alignment control.
In Japanese Published Unexamined Patent Application No. 2008-235900, a two-layer alignment film structure is described, wherein an alignment film capable of photo-alignment is formed in an upper layer and an alignment film having a lower volume resistance than the upper layer is formed in a lower layer, thereby shortening the time in which an afterimage disappears. In Japanese Published Unexamined Patent Application No. 2003-57147, a method for measuring azimuthal anchoring strength which becomes a problem in photo-alignment is described.